2006 Vauxhall Corsa gear change hard

My car problem geear ..when ingine of gear liver is good .iin every gear going simply...but when i on the road automaticaly suddenly gear liver too much hard ...more hard in 1.2.3 4..when i do ingine of and after some hours is good working but suddenly repeat same problem.some time is too much hard ...when i put car in back gear its crrrrunchy noise....please give me solution